1. Field of the Invention
The invention relates to a combined cooling plant/heat pump for use in motor vehicles for the cooling, heating and dehumidification of the vehicle interior by means of a ventilation system.
2. Related Technology
Ventilation systems of motor vehicles have to meet a number of requirements. First, the system has to be capable of heating the air entering the passenger compartment in cold weather. More and more, vehicles are also provided with air conditioning units that are capable of cooling the air entering the passenger compartment in hot weather.
When a an air conditioning unit is used for cooling purposes, it is possible, especially in the transitional periods between warm and cold seasons, to reduce the humidity of the air entering the passenger compartment. In doing so, the evaporator of the air conditioning unit is used for the dehumidification of the air, which then is heated by the heater core of the engine cooling circuit to the desired temperature. In this way it is possible to effectively prevent the vehicle windows from fogging.
As an introduction to understand the invention better, a typical state-of-the-art realization of this combined operation is represented in FIG. 1.
The engine cooling system 2, in its simplest form, includes a cooling circuit usually working based on a glycol-water mixture (the coolant), and a pump 12 that circulates the coolant through the engine or the driving aggregate 13 of the vehicle to a thermostatic valve 14, from where, depending on the demand, the coolant flows to either the heater core 5 of the ventilation system 3 or to the radiator 15, or both, after which the circuit is dosed at the pump 12.
The air conditioning unit 1 includes a compressor 6, which compresses a refrigerant, an exterior heat exchanger 7, an inner heat exchanger 8 on the high-pressure side of the system 1 and an expansion valve 9. After the expansion valve 9, the decompressed refrigerant flows into an internal heat exchanger/evaporator 4, which is positioned in the ventilation system 3 and which provides for the dehumidification of air 16 entering in transitional weather and the cooling of the air in warmer weather. The subsequent heating of the dehumidified and cooled air that is to enter the passenger compartment is also known as “reheating”. The direction of the airflow in the ventilation system 3 is indicated by the arrow 16.
After the evaporator 4, the refrigerant passes to an accumulator 10, where liquid and gas are separated from each other and stored, and to an inner heat exchanger 11 on the low-pressure side of the system 1, and finally flowing to the compressor 6 closing the circuit.
Existing systems that present a combined cooling plant and heat pump for automotive vehicles are also known. Such a system is shown in FIG. 2.
In the system of FIG. 2, the refrigerant circuit of an air conditioning unit 1 is combined with the engine cooling system 2 and the ventilation system 3 of the vehicle. In this case the cooling circuit of the engine cooling system 2 is extended by a coupling heat exchanger 17 arranged between the refrigerant circuit and the engine cooling circuit as a further consumer or user of the engine's heat energy. This coupling heat exchanger 17 exploits the heat of the engine cooling circuit to evaporate the refrigerant of the refrigerant circuit and therefore provides the air conditioning unit with this heat as evaporation heat.
For the reheating operation in the air conditioning mode, the cooling circuit of the engine cooling system 2 is used in both systems. For that a heater core 5 is provided. Thus during operation of the air conditioning unit 1, air is dehumidified by the evaporator 4 and then heated by the heater core 5.
In the heat pump mode, heat of the engine cooling system 2 is transferred via the coupling heat exchanger 17 to the refrigerant circuit of the air conditioning unit 1 which supplies the heat to the air flowing into the passenger compartment in the internal heat exchanger 4 functioning as condenser/gas cooler. For a highly efficient and dynamic system, it is advantageous if the air 16 flowing into the passenger compartment does not pass the heater core 5 in this operational mode. This is achieved through a valve position in the air distribution chamber of the ventilation system 3, also known as the heating, ventilation, and air conditioning (“HVAC”) system.
In this case, the air conditioning unit 1 or the engine cooling system 2, respectively, is extended by the coupling heat exchanger 17 and corresponding switching valves and other components compared to the previously mentioned system.
The systems described above have the disadvantage that the heat exchangers needed are very expensive and their usual design versions take up a lot of space, which is very disadvantageous for mobile applications.
It is the objective of the invention to modify a device such that the task of heat exchanging in the ventilation system of a vehicle is realized in a space-saving way.